Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$225.87	3.504%	$233.7845	$233.78	$233.80	$233.80
Purchase #2	$203.59	9.426%	$222.7804	$222.78	$222.80	$222.80
Purchase #3	$168.67	9.843%	$185.2722	$185.27	$185.25	$185.30
Purchase #4	$29.74	7.213%	$31.8851	$31.89	$31.90	$31.90
Purchase #5	$100.61	9.583%	$110.2515	$110.25	$110.25	$110.30
Purchase #6	$192.63	10.731%	$213.3011	$213.30	$213.30	$213.30
Purchase #7	$27.42	4.794%	$28.7345	$28.73	$28.75	$28.70
7 purchase totals =	$948.53		$1,026.0093	$1,026.00	$1,026.05	$1,026.10